Carbon material, carbonaceous material for battery electrode, and battery

Abstract

A scale-like graphite and carbon material for a battery electrode which is suitable for use as an electrode material for an aqueous-electrolyte secondary battery, wherein the ratio IG/ID (G value) between the peak area (ID) in a range of 1300 to 1400 cm−1 and the peak area (IG) in a range of 1580 to 1620 cm−1 by Raman spectroscopy spectra, in which an edge surface of the particle of the scale-like graphite is measured with by a Raman microspectrometer, is 5.2 to 100 and the average interplanar spacing d002 of plane (d002) by the X-ray diffraction method is 0.337 nm or less and optical structures of the scale-like graphite have a specific shape; the method for producing the same; a carbon material for a battery electrode and a paste for an electrode containing the material; and a secondary battery having excellent charge/discharge cycle characteristics and high current load characteristics.

The invention claimed is: 
     
       1. A carbon material for a battery electrode, comprising a scale-like graphite,
 wherein the scale-like graphite has a ratio I G /I D  (G value) between a peak area (I D ) of a peak in a range of 1300 to 1400 cm −1  and a peak area (I G ) of a peak in a range of 1580 to 1620 cm −1  measured by Raman spectroscopy spectra, in which an edge surface of a particle of the scale-like graphite is measured with a Raman microspectrometer, is 5.2 or more and 100 or less and the average interplanar spacing d002 of plane (002) by the X-ray diffraction method is 0.337 nm or less; 
 optical structures of the scale-like graphite observed in a rectangular field of 480 μm×540 μm under a polarizing microscope satisfy the following relationship:
   1.5 ≤AROP≤ 6 and 
   0.2× D 50≤( SOP×AROP ) 1/2 <2× D 50,
 
 
 when areas of the optical structures are accumulated from the smallest optical structure in an ascending order, SOP represents an area of the optical structure whose accumulated area corresponds to 60% of the total area of all the optical structures; when the optical structures are counted from the optical structure of a smallest aspect ratio in an ascending order of the aspect ratio, AROP represents the aspect ratio of the optical structure which ranks at the position of 60% in the total number of all the optical structures; and D50 represents a volume-based average particle diameter measured by a laser diffraction particle size distribution analyzer; and 
 a BET specific surface area of the scale-like graphite is 0.4 m 2 /g or more and 3.5 m 2 /g or less. 
 
     
     
       2. The carbon material for a battery electrode, comprising the scale-like graphite as claimed in  claim 1 , wherein D50 is 1 μm or more and 50 μm or less. 
     
     
       3. The carbon material for a battery electrode, comprising the scale-like graphite as claimed in  claim 1 , which is artificial graphite treated at a temperature of 2,400° C. or more and 3,600° C. or less. 
     
     
       4. A method for producing the scale-like graphite as claimed in  claim 1 , comprising a process of mixing the particles obtained by pulverizing calcined coke and the particles obtained by pulverizing petroleum pitch or coal-tar pitch and subjecting the mixture to heat treatment at a temperature of 2,400° C. or more and 3,600° C. or less. 
     
     
       5. The production method as claimed in  claim 4 , wherein a volume-based average particle diameter measured by a laser diffraction particle size distribution analyzer of the particles obtained by pulverizing calcined coke (D50) Dc is 1 μm or more and 50 μm or less, and the volume-based average particle diameter of the particles obtained by pulverizing petroleum pitch or coal-tar pitch (D50) Dp is smaller than Dc and is 0.01 μm or more and 25 μm or less. 
     
     
       6. The production method as claimed in  claim 5 , wherein Dc/Dp is 1.5 or more and less than 200. 
     
     
       7. The production method as claimed in  claim 4 , wherein the mass of the particles obtained by pulverizing petroleum pitch or coal-tar pitch is 0.5 mass % or more and 15 mass % or less to the total mass of the particles obtained by pulverizing calcined coke and the particles obtained by pulverizing petroleum pitch or coal-tar pitch. 
     
     
       8. The production method as claimed in  claim 4 , wherein by observing the optical structures of the calcined coke in a rectangular field of 480 μm×540 μm under a polarizing microscope, when areas of the optical structures are accumulated from a smallest structure in an ascending order, an area of an optical structure whose accumulated area corresponds to 60% of the total area of all the optical structures is 10 μm 2  or more and 5,000 μm 2  or less; when the optical structures are counted from a structure of a smallest aspect ratio in an ascending order, the aspect ratio of the structure which ranks at the position of 60% in the total number of all the structures is 1.5 or more and 6 or less. 
     
     
       9. A carbon material for a battery electrode, comprising 100 parts by mass of the scale-like graphite as claimed in  claim 1  and 0.01 to 200 parts by mass of natural graphite or artificial graphite, wherein an average interplanar spacing (d002) of the natural graphite or artificial graphite is 0.3370 nm or less. 
     
     
       10. A carbon material for a battery electrode, comprising 100 parts by mass of the scale-like graphite as claimed in  claim 1  and 0.01 to 120 parts by mass of natural graphite or artificial graphite, wherein an aspect ratio of the natural graphite or artificial graphite is 2 to 100, and an average interplanar spacing (d002) of the natural graphite or artificial graphite is 0.3370 nm or less. 
     
     
       11. A paste for an electrode comprising the carbon material for a battery electrode as claimed in  claim 1  and a binder. 
     
     
       12. An electrode comprising a molded body of the paste for an electrode as claimed in  claim 11 . 
     
     
       13. A battery comprising the electrode claimed in  claim 12  as a constituting element. 
     
     
       14. The carbon material for a battery electrode as claimed in  claim 1 , wherein, in an evaluation test of a battery fabricated as a three electrode cell by laminating a carbon electrode (negative electrode) comprising the carbon material, a positive electrode and a reference electrode, the ratio (change rate of the electrode thickness) (T500/T10) of the thickness (T500) in a discharge state after repeating 500 cycles of charge and discharge to the thickness (T10) in a discharge state after performing 10 cycles of initial aging is 1.0 or more and 1.30 or less. 
     
     
       15. The electrode as claimed in  claim 12 , wherein, in an evaluation test of a battery fabricated as a three electrode cell by laminating the electrode (negative electrode), a positive electrode and a reference electrode, the ratio (change rate of the electrode thickness) (T500/T10) of the thickness (T500) in a discharge state after repeating 500 cycles of charge and discharge to the thickness (T10) in a discharge state after performing 10 cycles of initial aging is 1.0 or more and 1.30 or less. 
     
     
       16. The carbon material for a battery electrode, comprising the scale-like graphite as claimed in  claim 1 , wherein D50 is 1 μm or more and 25 μm or less. 
     
     
       17. The carbon material for a battery electrode, comprising the scale-like graphite as claimed in  claim 1 , wherein a BET specific surface area is 0.4 m 2 /g or more and 3.0 m 2 /g or less.